download Youtube Videos as mp4 I heard it will grab any thing
Here are the formats you can download using this extension:

* MP4 360p (480x270, 480x360) - all videos are available in this format. Use it if you want to play videos on an old mobile phone (iPhone 3GS, HTC Desire, Samsung Galaxy S2) or to save space.
* MP4 720p (1280x720) - HD format, available for an increasing number of videos. Use this format if you want to play higher quality videos on a tablet, laptop or a phone with HD display.
* just in case you need it, you can also download the highest-quality FLV version available: FLV 240p (426x240).
* 480p and 1080p are no longer available as standalone videos downloaded from youtube.com. YouTube switched to adaptive streams and uses separate files for video and audio, which need to be merged to get a video file. This is more complicated and requires more advanced tools (ffmpeg), so I haven't added them yet.